System of synchronizing signaling apparatus



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Original Filed Feb.26, 1925 4 Sheets-Shef- 3 41 ast ATTORNEY 4 Sheet s-Sheet rATTORNEY A. L. MATTE SYSTEM oF sYNcHnoNIzING SISNALING APPARATUS original Filed Feb. 26, 1925 4.9" nun.

Patented Oct. 18,k l19,27.

UNITED STATES PATENT OFFICE.

ANDREW L. MATTE, OF BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION 0F NEW YORK.

SYSTEM OF SYNCHRONIZING SIGNALING APPARATUS.

Application filed ebruary 26, 1925, Serial No. 11,801. Renewed May 20, 1927.

An object of my invention is to provide a new and improved system of synchroniz ing apparatus `at points between which an electrical transmission is effected. Another object of my invention is to provide for proper synchronous relation of the currents in the various parts of an electric signaling system. Another object isv to provide for synchronizing by currents of suitable frequency, more particularly to synchronize re latively low frequency apparatus lby transmission of higher frequency currents. Still another object is to govern the frequency of a-vacuum tube oscillator by impressing a current of harmonic frequency thereon. These and various other objects of my invention will become apparent on consideration of several particular embodiments of the invention which I have chosen for illustration and which I now present by way of example in the following specification taken with thev accompanying drawings. It will be understood that the invention is defined in the appended claims and that the following description relates more particularly to the examples shown in the drawings.

Referring to the drawings, Figure 1 is a diagram illustrating a transmitting and receiving station which may be called West; Fig. 2 is a diagram illustrating the correspondingl cooperating station which may ybe called East; Figs. 3 and 4 are wave train diagrams that will be referred to in explaining the mode'of operation of the system of Figs. 1 and 2; and Figs. 5 to 9 are diagrams illustrating modifications In Fig, 1 a-local traced from ground 11, through the condenser and resistance in parallel and through the windings of the relays G0, G1 and' S1, armature and contactof relay G0 to the battery and ground 12. This circuit. with its condenser and resistance in parallel, causes periodic. vibration of the armature of the relay G0 with accompanying alternating current through the circuit, and accordingly the armatures of the other two relays G1 and S1 will vibrate at the same frequency.

The vibration of the armature of relay G1 y sends an alternating Icurrent through the primary of the transformer 13 and induces a corresponding current in its secondary.

.This current will have approximately the wave form shown in Fig- 3,` composed Qt a equivalent device.

circuit may be readily The phase splitter N1 comprising the coni denser 14 and resistance 15 splits each of these simple components into two phases 90 apart, lmpressing the corresponding electromotive forces across the filament and grid of the respective vacuum tubes 16 and Since these tubes draw substantially no currentfrom the input circuits, there will' be substantially no reaction on the phase splitter, and the output currents from the vacuum tubes 16 and 17 will be in the proper 90?- relation for the two components of each of the component frequencies, the fundamental and the odd harmonics.

The output currents from the vacuum tubes 16v and 17 go t'o respective attenuation equalizers E which brins,r the different frequency components to ay desired intensity relation. From there the currents go to respective amplifiersy A and' are 'put on the respective conductor pairs 18 and 19 to which band filters BF are'connected in multiple'. Each band filter BF passes only one of the harmonic frequencies.

Each harmonic component passed by a re-' spective'band filter goes to a respective sending network SN controlled by a keyor Thev signal wave trains from each sending network SN go through a respective band filter SF and thence in multiple to the common conductor pair 2O and to the line W. I

It will be seen that the various carrier currents on the line W1 differ not vonly in frequency, being all harmonics of a single fundamental, but that for each frequency there are two components 90o apart in phase, one component put on through the .conductors 18 and the other through the conductors 19. All these component currents are modified to form signals by means of the sending networks SN except that one component in one phase is appropriated for securing synchronism at the station "East; the otherl phase of the vsame frequency is suppressed. The sending network for the synchronizing channel is controlled, not by a regular signaling network but by the relay S1, so that the carrier current wave train in this channel is interruptedregularly at the frequency of the fundamental, and a fixed phase relation lis obtained between modulating and modulated waves. Accordingly in this channel regular interrupted Wave trains are sent, as shown in Fig. 4.

At thestation East the currents received from the line lV, go through the conductors 23 to respective band filters RF which pass the respective frequencies. These currents then go through suitable phase adjusters PE to the respective detectors D1 and D2 whose output currents control the receiving polar relays R2 and R2. The detectors vDl and D2 also receive currents .of the same frequency but a quarter phase apart over the conductors 27 and 28 from a source that will be pointed out presently. One of these locally generated currents corresponds in phase with one phase of signal current, and the other locally generated current corresponds in phase with the other phase 4,of signal current, and therefore, one phase of signal current is detected in one detector Dl and the other, in detector D2.' For these detectors D1 and D2 local currents of the same frequency as the respective carrier currents and in proper phase relation are required. These are supplied over the respective circuits 27 and 28, and their generation in the proper phase relation will now be described."

One of the receiving filters RF connected With the conductors 23 passes the regularly interrupted Wave trains controlled at the sending end by the relay S1 and pictured in Fig. 4. These wave trains go vto the del' tector D3, Whose output controls the relay G2, Whose armaturel accordingly vibrates regularly and puts a current on the circuit 40 corresponding to the diagram of Fig. This current passing through the primary of the transformer 26 generates a current in its secondary Which goes to the phase splitter N2, from which point the operation is the same as for the phase splitter N1 at station West i Accordingly the various band filters BF at station East deliver currents corresponding in frequency to the various harmonics described as generated at station West and in two phases D apart for each such harmonic. These currents go on through suitable sending networks and sending filters to the line W2 from East to West, as already described for the line W1, from West to East Also before going through the sending networks, branch circuits such as 27 and 28, are taken off leading to the respective detectors 'D1 and D2 and furnishing the locally generated currents suitable to the method of 'reception here employed.

At station West the currents received over the line V2 go to receiving apparatus similar to that at station East, as indicated by the box Y which corresponds to the apparatus Within the dotted enclosing line marked Y at station East. The locally generated currents for Y at West are obtained by conductor pairs 30 and 31 from the outputs of the band filters BF.

In connection with many transmission lines, it is not practicable to transmit a low frequency; in other words, the line will cut off frequencies below a certain limit, and if it were attempted to transmit the unmodul modulated by the fundamental frequency,v

and then at the receiving end it is demodulated to obtain the fundamental frequency. Also it will be noticed that the operation of the apparatus involves a definite relation in phase and frequency between the fundamental and the various harmonics. Vhatever the fundamental frequency at the station Vest, it willA be exactly the'same at the station East, and, moreover, the various harmonics at both stations will be precisely harmonic to that fundamental frequency and in definite phase relation with the fundamental. A fourwire carrier telegraph system using phase discrimination requires that rather precise phase relations be maintained among the currents at various points of the system. Accordingly my invention finds useful application in such a system, and l have disclosed such a system in F igsl 1 and 2.

Referring to Fig. 5, this shows a modiiication as compared with Figs. 1 and 2. The apparatus enclosed within the dottedrectangle X of Fig. 1 is represented by the simple box X in Fig. 5, and similarly the apparatus Y of Fig. 2 is represented by the box Y in Fig. 5.

The vacuum tube oscillator 40 of Fig. 5 transmits its output through the transformer 41 to the harmonic generator or distorter H. The device H is Well known as an element which will distort the wave form of a simple alternating current of a certain basic frequency so as to make it rich in harmonics, which may then be separated to variouschannels as already explained for the apparatus X in Fig. 1.

\ One of the harmonic frequencies from the apparatus X is taken off over-the. conductorsv 43 through the band filter BF to the modulator M where it is modulated by the fundamental frequency taken froln the oscillator 40 through the transformer 42. The modulated output goes through the Jsending filter SFl and over the line Wl to the station East. There the various frequencies are separated by band filters in the apparatus 1 Y except that the same frequency as in the X similar to X in Fig. l. From X the various harmonics go over separate pairs quency conductors 43 at the sending station goes through the conductors 45 to an appropriate band filter BF and to the detector D where the fundamental frequency is detected and passed through the low pass filter LPF and amplifier A to the distorter H and apparatus of conductors like 27 and 28 to the receiving apparatus Y for reception, and currents of the same harmonic frequencies are mod ulated in the apparatus X for sending messages and transmitted from East to WVest over the line W2.

In Fig. 6 the particular harmonic frequency appropriated for synchronizing is put on the line W1 without being modulated and is transmitted as a ure unmodulated current of the harmonic requency. At the receiving end this current goes through the appropriate band filter BF to a modulator M. Its frequency is ml where d is the fundamental frequency and a is a positive integer.

The modulator M also receives from a local source, as will be explainedl presently, a current of frequency (nil) d, and therefore in the output `from the modulator M there is a component of frequency d. This component only is passed by the low pass filter LPF Whose output is connected to the input of the vaccum tube oscillator 46.

This oscillator 46 is adjusted so that its natural frequencyis as nearly as'practicable equal lto the frequency d. Therefore when the frequency d is impressed onits input, the oscillator 46 will be forced to exactly that frequency.

. The output from the through the transformer 47 and the distorter H to t-he apparatus X from which the line W.l leads from Vest to East. Also from X in separate circuits, such as 27 and 2,8, the locally generated harmonic frequencies are taken to apparatus Y for reception.

Furthermore, by means of the conductors 48,l

one such locally generated harmonic current of frequency (wind goes to the modulator M where its effect has already been eX- plained.

In Fig. 7 the vpure harmonic `frequency current for -synchronizing is put on the line at station Iest, the s ame as in Fig. 6, but at station East the received current of this frequency is not put through a modulator but is applied directly to the input of the vacuum tube oscillator 46. The natural freof this oscillator 46 is as nearly as practicable adjusted to be equalto d, whereas the input frequency is mi. The application of the harmonic frequency mi to the input of 'this oscillator adjusted rather closely to the naturalv frequency CZ forces the said oscilla- 'tor to operate at precisely the frequency d.

The output from the oscillator 46 goes oscillator 46 goes through the distorter H and the apparatus X which operate in the manner already described for those elements in earlier figures of the drawings.

In Fig. 8 at station West two different harmonic frequency components are taken off through the conductor pairs 43 and-48 and are superposed on the line W1. lAt station East these are passed through the conductor pairs 45 and 45 and appropriate band filters BF, and then these harmonics are combined in a beat rectifier whose Acomponent of lowest frequency will be the difference of frequency between the two harmonics already referred to. This difference is equal to the fundamental frequency of the system and is passed by the low pass filter LPFto the amplifier A Whose output goes through the distorter H to the apparatus X where its effect and utilization are as already described for similar apparatus X and X in other figures of the drawings.

At station IVest vacuum tube oscillators such as 48, 48 and 48 are coupled successively through the resistances such as 49 and 49". These oscillators are adjusted as nearly as practicable so that thenatural frequency of one of them is a certain comparatively low frequency fundamental, and the others are harmonics 1 thereof. By virtue of the couplings through the resistances such as 49 and 49 the battery of oscillators are forced so that they operate precisely at the harmonic frequencies just mentioned and which would be realized only approximately if the oscillators had no connection with one another.

cillators are taken off across the resistances such as 49, 49 and 49 and the condensers 95, etc. These are respectively in quarter phase relation, and each pair of quarter phase voltages are impressed upon the grids of two push-pull vacuum tubes which, presenting a substantially infinite impedance to these voltages, draw no current and, therefore, do not disturb the phase relation. The output currents of thesel respective phases are led to sending networks through separate independent transformers where 1 they are modulated in the manner described eartwo harmonic frequencies in Fig. 9 a plurality of The various voltages from the various yoslier and then transmitted through sending 49", and after passing through the lilter SF is put on the line without having any message signals impressed thereon.

At the station East this last mentioned particular harmonic frequency goes overthe conductor pair 45 through an appropriate band filter BF to the transformer primary 53.

The battery of oscillators such as 50,50 and are adjusted as nearly as practicable to have the same natural frequencies as the respective oscillators at the station IVest such as 48, 48 and 48". One of these oscillators 50 is adjusted to have as nearly practicable the same frequency as the oscillator 48 from which the pilot frequency for synchronizing purposes was drawn. The input circuit of the oscillator 50 comprises a coil .52 which is made the secondary to the primary winding 5i?) already mentionedl Thus the synchronizing frequency transmitted over the' line W, is applied to the oscillator 50 and forces 1t to operate precisely at that frequency. Then by virtue of the resistance couplings between successive oscillators such as 51 and 51, the whole battery of oscillators at station East is forced to operate at the same respective frequencies as'for the oscillators at station Vest The output circuits from the .respective oscillators 50, 50', etc., go through filters and sending networks for transmitting over the line 72, and also by branch circuits such as 27 and 28 these frequencies go to the apparatus Y where they are employed for re ception.

I claim:

1. In combination,a transmission line incapable of transmitting currents of relatively low frequency, apparatus at two places to be synchronized at a relatively lo'w fr equency, means for generating a harmonic current at one of those places and transmitting it over said line and applying it at the other place to synchronize the apparatus thereat With the apparatus where the said harmonic current was generated, means for generating other harmonic currents at one of those places and transmitting them over said line, and means for phase-splitting each of said other harmonie currents and transmitting and receiving respective Vmessages on the resultant components.

2. In a multiplex carrier current system, a line, means to generate a composite alternating current of a certain fundamental frequency and to separate the component curients of other frequencies to respective channels associated With said line, means at the sending end to modulate one of the higher frequency component currents at the rate of the fundamental, means at the receiving end governed by the said currents so modulated to control the generation of a current corresponding to the composite current generated at the other end of the line, and means to separate the component currents of other frequencies to respective channels at said other end of the line and transmit them in the reverse direction.

8. In a multiplex carrier current system, a line, meansat one station on the line to generate alternating currents of various frequencies and to separate them into respective channels and modulate them respectivelyfor signaling and to modulate specially one such component current at the rate of the lowest frequency and to put all the modulated currents on said line, and

means at another station on the line governed by said specially modulated current to generate a set of currents for sending in the reverse direction and for homodyne reception.

4. In a multiplex carrier current system, a line, means at one station on the line to generate a composite alternating current of a certain fundamental frequency, means to separate its components to various conductors and to modulate them for signaling and specially to modulate one such component `regularly at the rate ofthe fundamental alternating current and to put all the components so modulated on the line, and means at another station controlled by said specially modulated component current to generate an alternating current like that generated at the first mentioned station, and in definite phase relation therewith whereby its components will also be in definite' phase relation with the said components of the current generated at the first mentioned station.

5. In a multiplex carrier current system, a line, means at one station on the line to generate-a composite alternating current of a certain fundamental frequency, means to separate its components to various conductors and to modulate them for signaling and specially .to modulate one such component regularly at the rate of the fundamenta-l alternating current and to put all the components so modulated on the line, and means at another station controlled by'said specially modulated component current to generate an alternating current like that generated at the first. mentioned station, and means to utilize said alternatin current generated at said other station for multiplex sending in the op osite direction.

6. In a multip ex carrier current system, a line, means at one station on the line to generate a composite alternating current of a certain fundamental frequency, means to separate its components to various conducmodulate one such component regularly 'at the rate of the fundamental alternating current and to put all the components so modulated on the line, and means at another sta-- tioncontrolledby said specially modulated component current to generate an alternating current like that generated at the firstmentioned station, and means to utilize the components of--said alternatin current enerated at said other station or homo yne reception thereat. y

7. In a multiplex carrier current system, a line, means at one station on the line to generate a com osite alternating current of a certain fun amental frequency, means to separate its components to various conductorsand to modulate them for signaling and specially to modulate one such component regularly at the rate of the fundamental alternating current and to put all the components so modulated on the line, and means at another station controlled by said specially modulated component current to generate an alternating current like that generated at the first-mentioned station, and means to utilize the componentsof said alternatinv current generated at said other station For homod ne rece tion thereat and for multiplex sen ing in tlie opposite direction.

8. In a multiplex carrier current system, a line, means at one station to generate a ^co` osite-,alternating current of a certain fun amenta-l frequency, means to separate its components to various conductors both according to frequency and according to phase and to modulate them for signaling and specially tomodulate one such component regularly at the rate of the fundamental alternating current and 'to put all the components so modulated on lthe line, and vmeans at another station controlled by said specially modulated component current to generate an alternating current like that l,generated at the rst-mentioned station.

In testimony whereof, I have signed my name to this specification this 25th day of February, 1925.

ANDREW L. MATTE. 

